GNU Compiler Collection version 13 receives AMD Zen 4 CPU tuning prior to release

Jan Hubicka, SUSE compiler engineer, added more AMD Zen 4 code, specifically “znver4” to set the target for the CPU, to continue preparing the GNU Compiler Collection (GCC 13) for release.

GCC 13 sees additional and improved AMD Zen 4 CPU target tuning in the latest compiler update patch

This continues with many patches added in 2022 for the release of the new version. Predictably, it will be better for the AMD Zen 4 architecture than the support shown for Zen 3, which was mediocre at best. We’ll also see new ISA processor extensions used for the latest build, reports Michael Larabel, analyst, and editor at the Phoronix site for Linux hardware.

Yesterday Hubicka added the latest updates for GCC 13, for which we’ve provided the patch notes below and posted on the GNU Compiler Collection’s Git page:

This patch adds more beats for zen4:

  • New avx512 scatter tones for instructions.
    • In micro benchmarks, these appear to be flat losses compared to losses with an open cryptocurrency
  • Disable pool use for zen4
    • While these are a win for micro-standards (based on TSVC), enabling aggregation is a loss for parity. So, for now, it seems safe to keep him out.
    • Disable scrolling to avoid FMA strings for znver4 since fmadd is optimized and doesn’t seem to cause regression.

Larabelle notes that the AOCC 4.0 compiler for GCC 13 and AMD will be required to test to see which is better “as a downstream LLVM/Clang.” AMD recently added initial enabling of Zen 4 architecture in LLVM/Clang early last month, but it hasn’t been touched upon since. We hope to see more in the coming weeks.

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The Phoronix editor also mentions that “-march=znver4 can be used if you want to cater for compiler instructions and optimizations for AMD Ryzen 7000 series and AMD EPYC 9004 series processors”. At the same time, we are waiting for more updates to happen.

Lately, it seems that AMD has put a heavy emphasis on making AMDGPU for DRM-Next, as reported yesterday. Many of the targets weren’t initially supported, and it’s good to see that work is now being added on upcoming patches within the various open source projects to prepare for Q1 releases.

News source: Phoronix

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